Picture transmitter



Oct. 18, 1938. c. A. CASTRO PiCTURE TRANSMITTER Filed Jan. 2,v 1935In;52.55.55%? H as I m Cesar A, Cas+ro INVENTOR BY g 4;, ATTORNEYPatented Oct. 18, 1938 UNITED STATES PATENT OFFICE 2 Claims.

This invention relates to electromagnets generally and more specificallyto those usable in television systems for the discharge of the electriccharges stored in the photocells forming thephoto-electric-light-sensitive screen. To effect the discharge, insequence, of the minute photocells forming the light-sensitive screenseveral methods have been proposed in the past including two types ofelectronic discharge. In one of these methods a pencil of light scansall points of the screen in order to cause a discharge of electrons withvariable potential according to the intensity of the photoelectriccharge stored in each individual cell, the separate discharges beingcollected by a suitable anode for transmission in the usual way. In theother method instead of using a pencil of light an electronic ray from acathode tube is employed to neutralize the positive charges in the cellsand discharge the series of cells in sequence through a suitableconductor.

-Neither of these methods has proven entirely satisfactory in practicebecause both the light pencil and the electronic ray, probably due todispersion of the particles or for other reasons, will cover severalphotocells at the same time and, therefore, their discharge is noteffected in perfect sequence. The result is that the reproduced imagelacks the necessaryresolution or detail.

With the foregoing in mind, one of the principal objects of thisinvention is to provide electromagnetic means by which the discharge ofthe photocells forming the light sensitive screen is effected in perfectsequence due to the fact that the cells are discharged under theinfluence of the E. M. F. created by the wave flowing through the magnetWinding opposite the cell rows in similar formation.

Another object of the invention is to provide .g a novel type ofelectromagnet, mainly for use in connection with television systems, foruniformly discharging the photocells forming the sensitive screen of atelevision transmitter.

Still another object of the invention is to prov? e eiectro-magneticmeans to reproduce in the receiver of a television system the modulatedcurrent received from the transmitter for the conversion of the electricimpulses into light.

Other objects and advantages of the invention will be come apparent fromthe following description and appended claims taken in connection withthe accompanying drawing, in which:

Fig. 1 is a perspective end view of the electromagnet made in accordancewith this invention;

Fig. 2 is a perspective front view of the same electromagnet;

Fig. 3 is a diagrammatic view of the electromagnet of this inventionassociated with other parts of a television transmitter.

Fig. 4 is a perspective lateral view of a modified form of electromagnetembodying the principles of this invention;

Fig. 5 is a front view, partly broken away, of a light-sensitive screenadapted for use in connection with the electro-magnet according to thepresent invention.

Referring now to the accompanying drawing and in particular to Figs, 1and 2, the numeral Hi indicates the core of the electromagnet, made ofmagnetic or other suitable material. numeral l4 represents thewinding ofthe magnet and to simplify the illustration only a few turns of themagnet are shown.

According to the present invention, the discharge of all the minutephotocells I6 is effected in absolute sequence due to the fact that theysuccessively come under the influence of an instantaneously createdelectromagnetic field by following the path of the wave crest flowingthrough the electromagnet winding l4. This action is similar to that ofan induction coil and for this reason I call the magnet of this in'vention an induction electromagnet. The latter comprises a core [0consisting of a flat plate of magnetic or other suitable material,either of. open pole or of closed magnetic circuit type; the winding I4is preferably made of a single layer of wire closely wound in a numberof turns equal and parallel to the lines or rows of photocells Itforming the light-sensitive television screen 16 which will be morefulls. described hereinafter.

In Fig. 3 the electromagnet or the present invention is shown associatedwith other parts of a television transmitter of any suitableconstruction, in which the numeral I 6 indicates the usual lightsensitive screen, 25 indicates the anode, l8 represents a lens or glassplate forming a part of the photographic device I8, 26 indicates theframe of the apparatus, 22 is one of the threaded bolts used to securethe photographic device upon the frame 20, and 24 denotes the back wallof the apparatus shown. The electromagnet is placed in magnetic contactwith one of the surfaces of said light sensitive screen l6 in order thatall the photo-cells l6 may be under the direct influence of the inducedmagnetic flux or E. M. F. for the sensitive discharge of the photocells.The light sensitive screen 16, shown in Fig. 5, comprises a series ofphoto-electric cells The" all

such a way as to present a number of turns equal and parallel to thelines or rows of photocells forming the light sensitive screen.

The operation of the electromagnet of the present invention and itsinfluence upon the light sensitive screen are described in thefollowing: Whenan object is placed in front of the photographic deviceit, illustrated in Fig. 4, the individual photoelectric cells I6" of thelight sensitive screen it become electrically charged in accordance withthe light valuesof the object. The winding ll of the electromag'net isconnected to a source of current (not shown) and the current interruptedintermittently; Eachi'nterruption of the current flowing through thewinding 4- of the electromagnet will set up an electromagnetic field andas a result induct-ion cur-rents will flow from the photoelectri'cce'll's- I6 through the surrounding dielectricinsul'atingmaterialof thescreen l6'to the conductor 26 leading to the amplifier. Themomenta-current thus produced will be of vary- 7 ing intensity dependngupon the charges of the photoelectric oells-whichinturn correspond tothe different light values'of theobject. My electromagnet isconstructedin suchmanner that each tumofthewinding Mlies parallel withand corresponds to a row of photoelectric cells IS. The electric currentflowing through the first turn of the winding l4' thus causes thedischarge of the firstrow of photoelectric cells I6 and when the currententfersinto'and flowsthrough the secondturn of the winding Hi, thesecond row of cells I6 are discharged-and soon. As the current flowsthrough each turn of the winding H the individual cells 16 dischargesuccessively their resp'ectivecharg'e'sand inasmuch as the winding I4comprises exactly the same number of turns as there are rows of cellsIS, the latter are always discharged in proper sequence.

In connection with the receiver of a television system, the inductionelectromagnet of this invention is placed adjacent to the receiver platepreferably formed of lines or rows of conductive cells or wirescorresponding to the lines or rows of photocells forming the transmitterlight-sensitive screen (Fig. The modulated current intermittentlyflowingthrough the induction electromagnet will create relatively strongelectric impulses in the conductive cells or wires of the receiver plateand these electric impulses may be converted into light for thereproduction of the view-or image'in any manner well known to the art.In my co-pending application Serial No. 71-9576 areceiver plate formedof a mosaic of wiresis'disclosed, which may be well adapted to use inconnection with the induction electromagnet of the present invention.

Various modifications and changes may be made in uie' apparatusdescribed withoutdepartme from the" spirit of the invention and,therefore, my inventionshould be interpreted as includin'g such-changesand modifications with no other limitations than those derived from thescope of the'appended -claims;

1.An induction-electromagnet adapted for use a in a te'levision systemcomprising a light-sensitive screen fo'rmed of aplurality of photocells,said electmmagnet comprising an angular core having at-leastone-flat',relatively wide side and a winding of covered wire closely wound carriedby said core on the saidflat side thereof, said flat side being disposedadjacent to the said screen.

2-; In a t'elevisio-n system,the combination of a light sensitivetelevi'sion screen comprising a plurality of photoelectric cellsdisposedin rows with an electromagnet consisting of a core and a wirewin-ding thereon;- each turn of the winding corresponding to a rowofcells and being disposed parallel thereto and conductive means adjacentsaid" cells; said electromagnet and screen being i'ri electromagneticcontact with each other and spaced apart to establish a gaptherebetween.

CESAR A. CASTRO.

